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The paper deals with the energy transition, focusing on the decisions to be taken about the change in the energy conversion capacity of specified portion of the universe, such as industrial or domestic districts, regions, countries, etc. Conversion capacity is intended here as the set of all energy conversion and storage units characterized by type, size and number, and interacting with the natural gas and electricity grids. The goal is to find guidelines for new installations, obtained by simulations of a model able to describe properly the behavior of each energy conversion technology and the interaction with grids. The model is based on a traditional MILNP approach, but contains unique features in the literature, which allow to obtain results of general validity for applications to very different geographical areas, or to countries including very different regions that transmit energy with each other or export/import it from abroad. The main novelty of this work is to identify the best planning for the decarbonisation of energy demand sectors, according to the criterion of minimum cost, both at global and at regional level. The results applied to the case of Italy allow identifying clearly the energy demand sectors to which new installations should be applied first to minimize the cost for the total energy system, and the units that must be foreseen to satisfy these energy demands, i.e. a precise strategy for the energy transition towards a 100% renewable system. • A multi-regional model is built to find the most convenient energy transition path. • General guidelines for Western countries are derived from the Italian case study. • Replacement of boilers with heat pumps allows increasing RES share from 20 to 30%. • For RES share >60%, PtG is the low-carbon strategy for high temperature heat demand. • Transportation is the last energy sector that should be decarbonized. [ABSTRACT FROM AUTHOR]

This paper aims at evaluating the best allocation of potential biomethane generation for the decarbonization of the transport system, presenting a case study in Italy. The country has some peculiar features, such as several operating biogas plants, additional potential feedstock for biogas/biomethane generation, a well-developed natural gas network and established relevant natural gas uses in different final sectors, including transport. Based on current estimates for sustainable biomethane potential by 2030, ranging from 2.3 to 7.6 billion cubic meters depending on the scenario, the analysis compares technologies for the generation, distribution and final use of biomethane. The results of the analysis confirm the potential interesting contribution of biomethane in decarbonizing the Italian transport system: a billion cubic meters of biomethane can lead to 2.33–4.37 Mt CO 2 e savings, depending on the feedstock mix and the application. On a national basis, annual climate emission savings in 2030 range from 10.0 to 26.7 Mt CO 2 e , depending on the scenario. Additional 3.1–8.1 Mt CO 2 of emissions can be avoided if the CO 2 captured during the biomethane upgrading can be stored or reused. The proposed methodology could be used to extend the analysis to other countries, and to the European context. • We analyze the climate emissions of biomethane for different supply chains. • We evaluate the effects of feedstock, distribution strategy and electricity mix. • The results confirm the important role of biomethane for transport decarbonization. • We discuss the best allocation in transport segments based on emissions savings. • We compare alternative biomethane scenarios for Italy in 2030. [ABSTRACT FROM AUTHOR]

So far, energy planning methods faced several challenges in achieving a proper assessment due to the extreme variability of input conditions. To considerably decrease the computational efforts in achieving solutions, most of the analyses reported in the scientific literature assume constant costs and demand over the entire planning horizon in a typical year. However, results might not be perfectly aligned with real ones because of the incapability of some models to address several aspects like energy demand/production variability, energy and technology costs, efficiency degradation, and use of different energy carriers. This paper proposes a novel methodology that optimises both the long-term planning and short-term scheduling decisions in the management of a multi-energy carries community by means of a Mixed Integer Linear Programming model that also considers the modular design of technologies (e.g., technological devices selection from a discrete set of variants). Such a model has been applied to the case study of a University campus in Italy, whose historical demand data were used for its energy planning with a time horizon of 30 years. Three scenarios have been analysed: (i) the Business As Usual, (ii) the Sector-coupling scenario, and, finally, (iii) the Hydrogen deployment one. The results are obtained under different energy scenarios, showing the effectiveness of the methodology in dealing with multi-investment stages at different planning levels in a reasonable computational time. In particular, they showed that deploying more sustainable technologies would increase the cost of the electricity (between 43%–89%), while reducing other energy carriers' cost (about 60%) and lowering all energy carriers' carbon footprint (between 50%–80%). From a long-term perspective, (i) the use of sector-coupling technologies is beneficial from both economic and environmental points of view, and ii) dynamic variations of some parameters can strongly affect the deployment of high-cost technologies to be installed beyond 2030. • A novel multi-investment stage approach for multi-energy-carriers community is proposed. • Methodology validated on different energy-policy-driven scenarios with up to five energy-carries. • Manufacturer's datasheet-based size enables realistic modular design. • Automatic energy systems expansion aligned with fluctuating parameters. • Electricity cost increment (40%–80%) for the economic and environmental benefit of the other carriers (50%–90%). [ABSTRACT FROM AUTHOR]

[Display omitted] • Simulations provide reliable hydrogen production data for estimation of key indicators. • Hydrogen produced by electrolysis has larger EROEI than natural gas-based routes. • Green hydrogen appears the best solution in terms of LCOH for small-scale local production. • Green hydrogen performs better in terms of GWP, while other impacts should be improved. • TCO of hydrogen-fuelled vehicles is larger than diesel ones mainly due to purchase cost. Hydrogen is a versatile energy carrier and storage medium that may be employed in a variety of applications. According to the industrial processes used for its production, hydrogen may be labelled using different colours: (i) grey hydrogen, produced from natural gas using steam methane reforming (SMR), (ii) blue hydrogen, like the grey one, but with carbon capture and storage (CCS), (iii) green hydrogen, produced by water electrolysis using electricity from renewable sources only, (iv) "grid" hydrogen, produced by electrolysis using grid electricity. In this study, process simulation is used to solve material and energy balances, as well as to estimate capital and maintenance costs for each technology investigated. Then, process simulation outcomes are used to estimate three key performance indicators focusing on sustainability issues: the Energy Return on Energy Invested (EROEI), the Levelized Cost of Hydrogen (LCOH) and the Life Cycle Assessment (LCA). With reference to the case study of the Trieste port in Italy, the potential of synthesizing and utilizing hydrogen to fuel transportation activities within a port is examined. Based on the daily hydrogen consumption in fuel cells installed on locomotors and trucks, the design of the different processes considered is carried out, as well as their comparison in terms of EROEI, LCOH, and LCA. Furthermore, LCA and Total Cost of Ownership (TCO) evaluations for various hydrogen-fueled vehicles within the port are presented and compared to diesel-fueled ones to determine the impact of fuel-cell vehicles during operations. Results show that EROEI of hydrogen produced by electrolysis is larger than that produced by SMR with or without CCS. The LCOH for grey hydrogen is of the same order of magnitude of that of green or grid ones. The hydrogen compression step to 300 bar impacts on both energetic and economic performances. LCA indicates that the Global Warming Potential (GWP) of green hydrogen is at least half with respect to blue hydrogen, however other impact categories are less favourable. On the other hand, the TCO of hydrogen-fueled vehicles is higher than that of diesel-fueled ones, mainly because of the higher purchase costs. It is concluded that the methodology proposed in this paper, based on the evaluation of indicators at the design stage, is suitable for comparing hydrogen production processes. In addition, it is a powerful tool for policy decision-makers in defining the strategies for the development of hydrogen-based transport systems in port operations. [ABSTRACT FROM AUTHOR]

• Optimal design of multi-vector energy hubs in energy communities. • MILP model using a multi-objective function. • Application to a real case represented by a university campus. One of the main ways to reach the important targets of the European Commission in the energy field set by 2030 is to implement sustainable energy systems to cover electrical and thermal energy demands, as well as transportation needs, in urban areas. In the aforesaid scenario, multi-vector energy hubs consist of installing small and medium size power plants, mainly fed by renewable sources, and charging infrastructures for electric vehicles in sustainable urban districts. The optimal design of such systems can be faced from different points of view and using different methods, one of the most adopted being the development of mathematical programming algorithms typically aimed to minimize global costs and emissions. The contribution of this paper is to propose an innovative methodology to optimally design a multi-vector energy hub able to supply electricity and thermal energy, for space heating and cooling, to a set of buildings within a sustainable district acting as a local energy community. The developed mixed integer linear programming model is characterized by very detailed models of the technologies and by a multi-objective function which is proposed to evaluate the impact of the optimal solution on global costs and emissions. The proposed mathematical model is very comprehensive as it involves a wide range of energy technologies with detailed modelling by considering the impact of external ambient conditions and energy vector temperature values on the plant conversion efficiency, thus showing high replicability potential in real contexts. In the case study, the model is applied to a university campus in the North of Italy. [ABSTRACT FROM AUTHOR]

Climatic conditions strongly affect the energy performance of buildings, and due to the synergy between global climate change and the Urban Heat Island (UHI) effect, the climatic conditions inside and outside the city are highly different. However, weather data collected at airports are commonly used for building energy simulations and these data do not take into account real temperature distribution in cities. Many studies in the literature address the topic but mostly considering only a couple of urban and non-urban stations. In this paper, the urban climate in Rome, Italy, is analysed after monitoring of the air temperature and relative humidity in four selected neighbourhoods and one reference station from October 2014 until September 2017. Rome is characterised by a composite urban pattern and high variability of building types, of which the four selected areas are representative. The heating degree days decrease up to 18% and cooling degree days increase up to 157% in the urban area with respect to the rural reference and the area most affected by the UHI is the city centre. The UHI is more intense in summer than in winter (average increase between 0.7 °C and 1 °C); while the diurnal and nocturnal UHI depends on the season and the neighbourhood. Then, the energy performance of a representative apartment block and a typical office building was computed using the measured data. Regarding the predicted energy performance, comparing the four urban sites and the reference site, the UHI causes a reduction of heating consumption up to 21% in residential building and 18% in the office building. An increase of cooling consumption up to 74% is instead computed for the residential building and up to 53% for the office building. [ABSTRACT FROM AUTHOR]

The United Nations Framework Convention on Climate Change (UNFCCC) sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change. Besides the “flexibility mechanisms” defined by the Kyoto Protocol to lower the overall costs of achieving their emissions targets, The Voluntary Green House Gases (GHG) reduction projects can have a lead role in GHG reduction in “non Emissions Trading System ETS sectors”. Nowadays, the voluntary market is characterised by critical aspects, such as fragmentation, lack of accounting, monitoring and validation rules that have led to the low spread of voluntary emission reduction projects developed by local authorities in the European Union despite their high potentiality. The aim of this paper is to test the applicability of voluntary emission reduction projects in the public sector following a homogeneous and consistent pattern. A research has been performed at local level on 143 voluntary emission reduction projects implemented by Public Administrations in Northern and Central Italy in renewable energy, energy efficiency and transport sectors. The applicable standards and methodologies have been checked and the case studies have been analysed though a three-step process: Preliminary additionality assessment; Projects selection; Validation of the selected project. The assessment shows that energy efficiency projects, once overcoming additionality issues, are the most promising for public entities while renewable energy and transport projects resulted to be mainly affected by double counting problems and lack of reliable methodologies. [ABSTRACT FROM AUTHOR]

The paper analyzes data about recharge of electric cars in Rome during 2013 as a part of a national research project (P.R.I.M.E.). The electric vehicles were recharged through the public Enel Distribuzione recharging infrastructure. For each recharge, the initial and final time were registered together with the electricity absorbed from the grid. The total number of recharges was about 7700. The first step of the investigation is the statistical analysis of the distribution of recharges in daily time slots in order to analyze the recharge behavior of Italian drivers. For each day and for each time slot, literature data from the Italian national grid operator (Terna) were used to retrieve the energy mix used to produce electricity in that day and in that time slot. In the third step, electricity generation mixes were used to obtain emission factors for greenhouse (CO 2 ) and pollutant emissions (CO, NO x , HC and particulate). Using information about the electric consumption of vehicles registered in Rome, the emission factors in g/km were obtained and compared with the limits set by European legislation for conventional (gasoline and diesel). [ABSTRACT FROM AUTHOR]

• Modelling and simulation of the proposed novel V2B2 energy schemes. • Use of electric vehicles and renewable energy technologies in clusters of buildings. • Analysis of the electricity transfer among buildings through electric vehicles. • Comprehensive parametric analysis for the energy and economic optimization. • Energy and economic performance guidelines for design and operating settings. This paper focuses on the energy and economic analysis of the Building To Vehicle To Building (V2B2) concept, conducted through a comprehensive parametric and sensitivity analysis. The idea behind this novel vehicle to building energy management is to exploit the use of electric vehicles as energy vectors to exchange electricity among buildings with the aim to accelerate the development of a novel zero energy paradigm, while promoting the deployment of renewable energy sources, accelerating the widespread usage of electric vehicles, and streamlining the regulation of charging stations in our future communities. In order to evaluate the potentials of the proposed schemes, a comprehensive parametric analysis is conducted to size the design and operating parameters which maximize the self-production and self-consumption of building integrated renewable energy technologies at a cluster level. The paper investigates the energy and economic performance of different V2B2 energy management schemes including a residential building, an office building, and an electric vehicle, which feature a basic cluster of human-linked energy consumers. The study is conducted by means of a novel in-house developed dynamic simulation tool, suitably enhanced to model the system operation. Numerical results, obtained for a representative weather zone (Mediterranean climate of Naples, South-Italy), show that through the V2B2 scheme, a remarkable exploitation of off-site renewable energy production is achieved, producing a significant reduction of fossil fuel consumption from the grid. [ABSTRACT FROM AUTHOR]

• Identify the main design features of different microgrids around the world. • This paper explores the main issues arising from the development of a microgrid. • An attempt to define potential solutions to overcome the main technical issues. • It defines guidelines for practical implementation and operation of microgrids. A microgrid is a small portion of a power distribution system with distributed generators along with energy storage devices and controllable loads which can give rise to a self-sufficient energy system. From the utility grid side, a microgrid is seen as an equivalent generator that is able to seamlessly disconnect and operate autonomously once a fault affects the main grid. The design, installation and operation of such systems lead to dealing with a number of technical and operational challenges including control, protection and infrastructure requirements. To help designers and researchers address these challenges and draw potential recommendations for practical microgrid implementations, in this paper a review of the main design features of existing microgrids is undertaken, also in light of the experience gained during the realization of the Prince Lab microgrid at Polytechnic University of Bari, Italy. The main control functions required to guarantee an economic, reliable and secure operation of a microgrid are also reviewed. Finally, key practical guidelines for monitoring, operation and implementation of microgrids are provided. [ABSTRACT FROM AUTHOR]

Electrical energy consumption data accessibility for low voltage end users is one of the pillars of smart grids. In some countries, despite the presence of smart meters, a fragmentary data availability and/or the lack of standardization hinders the creation of post-metering value-added services and confines such innovative solutions to the prototypal and experimental level. We take inspiration from the technology adopted in Italy, where the national regulatory authority actively supported the definition of a solution agreed upon by all the involved stakeholders. In this context, smart meters are enabled to convey data to low voltage end users through a power line communication channel (CHAIN 2) in near real-time. The aim of this paper is twofold. On the one hand, it describes the proof of concept that the channel underwent and its subsequent validation (with performances nearing 99% success rate). On the other hand, it defines a classification framework (I2MA) for post-metering value-added services, in order to categorize each use case based on both level of service and expected benefits, and understand its maturity level. As an example, we apply the methodology to the 16 use cases defined in Italy. The lessons learned from the regulatory, technological, and functional approach of the Italian experience bring us to the provision of recommendations for researchers and industry experts. In particular, we argue that a well-functioning post-metering value-added services' market can flourish when: (i) distribution system operators certify the measurements coming from smart meters; (ii) national regulatory authorities support the technological innovation needed for setting up this market; and (iii) service providers create customer-oriented solutions based on smart meters' data. • Smart meters' data can open a market of post-metering value-added services. • Access to electricity exchange data must be granted through a dedicated channel. • CHAIN 2 is a reliable and effective PLC-based communication channel. • Post-metering use cases can be classified based on level of service and benefits. • The Italian post-metering market structure can be regarded as a successful example. [ABSTRACT FROM AUTHOR]

• Weather files defined with different methodology and dataset are compared. • Projections of climate changes are considered in the construction of weather files. • The case study is a residential building in a cooling dominated climate. • The composition of weather files greatly influences the energy performance prevision. • Traditional efficiency measures are not resilient for the expected climate changes. The methodology, the site and the dataset as well as the emissions scenario considered in the weather file definition influence the numerical evaluation of efficiency measures resilience. With a complete statistical and critical approach, the paper analyzes the importance of these aspects by means of a residential case study simulated in Benevento, a city of south Italy. Using data monitored from 2015 to 2020, a current weather file is built with different methodologies. The comparison indicates that there is not repeatability of the year chosen as a reference for the various months and thus the resolution of the building energy balance could bring different results. Some future climate projections are also generated on medium (2050 s) and long (2080 s) term considering different emission scenarios. With long term projection, the heating degree days are reduced also of − 21% meanwhile the cooling degree days are more than double compared with the current condition. This suggests a remarked transition towards a dominant cooling climate for Benevento. Moreover, when the climate change is considered, the insulation intervention and the installation of double glazed low emissive window is not resilient because the heating energy need decreases also of −56%, but the cooling energy need increases of + 62% (2080 s). If the efficiency measures include also the cool roof and the external shadings, the cooling demand could be reduced until –33% in some scenarios (e.g. RCP 4.5-50th percentile) and increased (+31%) in some others (e.g. 2080 s). [ABSTRACT FROM AUTHOR]

• A novel hybrid model used to forecast energy production in onshore wind farms. • Evaluation of wakes phenomena of wind turbines at different conditions. • Definition of an availability model of the wind turbine generator. • Comparison between corrective and preventive maintenance strategy for a real case study. • Conception of a novel key indicator for the preventive maintenance. The contribution of wind power systems to the reduction of the impact of fossil fuels sources has increased more and more during the last decades leading to a greater attention to the estimation of the performances of renewable power plants. However, forecast methods of productivity of onshore/offshore wind farms still suffer, in terms of accuracy, the innate variability of the energy resources and the effect of components failures. This paper proposes a novel "hybrid" approach for the estimation of the energy conversion of onshore wind farms. The model combines the Jensen wake mathematical theory with a stochastic dependability model, a Fault Tree, to better forecast the energy production. A new key index was conceived to optimize the preventive maintenance of wind turbines. This model was tested on a real case study, a wind farm (25.5 MW p) located in the south of Italy. Results were promising because the model achieved a twofold objective to improve the accuracy of the energy conversion forecast and to provide a support decision system for the activities of maintenance planning. [ABSTRACT FROM AUTHOR]

• Aging problem for a wall package with vacuum insulation panels is studied. • Measures of heat flux and temperatures for 5 years are compared. • Experimental and analytical elaborations are combined for finding the aging trend. • The aging curve is implemented in a case study by means of dynamic simulation tool. • Energy consumptions, environmental indices and cost savings are discussed. The lack of data on the aging rate, under real operating conditions, is one of the most critical aspects for the diffusion of vacuum insulation panels in the building sector. This problem is analyzed in this paper by means of an integrated experimental-numerical approach. The panels under investigation are characterized by micro-porous silica pressed powder core with an aluminum barrier layer, for a total thickness of 10 mm. These are the insulation layer of a wall made of autoclaved aerated concrete blocks (total thickness of 21 cm) placed in a test room located in Benevento (south Italy). The experimental analysis is focused on the monitoring of heat flux and temperatures in order to evaluate the performance by means of the comparison with the same wall without insulation and for the indirect determination of the aging after five years (2015–2020). Results indicate an increment of thermal conductivity of 10.6%. Moreover, basing on experimental data, a semi-empirical linear function is appropriate to approximate the aging trend. A numerical case study, that implement the obtained aging trend, shows that the increment of thermal conductivity of vacuum insulation panels brings a reduction of the expected energy saving of 3% after 15 years. This result is true for several European cities with heating dominated climates. [ABSTRACT FROM AUTHOR]

• Electricity and electrification is a viable solution for the energy transition. • Electricity triangle assures a consistent framework for the energy transition. • Multifaceted benefits: energetic, environmental and socio-economic. • Conceptualization of a set of metrics for impact assessment. • A real case study (Italy) considering its evolution up to 2050. Greenhouse gases along with pollution generated by the present energy paradigm widely based on fossil fuels are providing large impacts in terms of climate change and the health of human and biological systems at large. A shift in the energy paradigm, from fossil fuels to renewable energy, is urgently needed for nature and society. This is what we refer to as the energy transition. An old commodity – electricity – can play a new key role in the energy transition. That can happen through what we call the electricity triangle involving electricity generation from Renewable Energy Sources, exploitation of electricity as the main energy vector, and electrification of the final energy uses in all sectors. The possible deployment of the electricity triangle must be carefully assessed in all its possible implications, from technological, economic, societal and environmental perspectives. In this paper, we conceptualize the electricity triangle as a viable approach to the energy transition, and we propose a set of holistic metrics to assess its possible impacts. We apply the electricity triangle framework to the case of Italy based on sectorial studies on RES generation and electrification in building, industry and transport sectors. Our results indicate that Italy in 2050 has the potential to achieve 85.6% penetration of RES in its electricity supply, while 41%, 53% and 42% of the energy consumptions in transport, residential, and industry sectors will be electrified. Ultimately, this would lead to a 68% reduction in CO 2 emissions compared to current levels. [ABSTRACT FROM AUTHOR]

• A modified exergy costing approach is assessed for advanced exergoeconomic method. • Auxiliary costing mode has indispensable effects on advanced exergoeconomic results. • Incorporating energy levels of streams can enhance advanced exergoeconomic analysis. • Thermo-economic losses in the real ORC plant are more of endogenous than exogenous. This study concerns advanced exergoeconomic analysis of a hybrid solar-biomass organic Rankine cycle (ORC) cogeneration plant. The hybrid plant had been previously conceived as structural optimization scheme to upgrade thermo-economic performance of a real 630 kW solar-ORC plant which currently runs in Ottana, Italy. The irreversibility rates, investment cost rates and irreversibility cost rates were obtained for each system component, based on thermodynamic balance as well as cost balance and auxiliary equations established for the components. Next, the avoidable/unavoidable and exogenous/endogenous splitting options were applied to investigate the sources of thermo-economic losses in the system, the effects of component interactions on the losses, as well as the best approach to improving the system. The main contribution of this paper centers on modification of the traditional auxiliary exergy costing in advanced exergoeconomic methodology, by incorporating stream energy quality into the cost formation process. Results showed that more than 50% of total irreversibility rates can be avoided in almost all of the components of the hybrid plant, most of which are endogenous. Similarly, it was obtained that component interdependencies have little impact on thermo-economic losses. Specifically, more than 60% of irreversibility cost rates could be avoidable in the hybrid plant by optimizing internal operations of each of the system components individually. Moreover, results showed that how auxiliary exergy costing is defined in advanced exergoeconomic method plays a significant role on the analysis, and the modified approach presented in this study is a viable choice. [ABSTRACT FROM AUTHOR]

• A bottom-up methodology to develop cooling load profiles in wineries is proposed. • The use of seasonal performance indicators to assess energy savings is discussed. • The proposed approaches are applied to a medium-scale winery located in Italy. • Annual distribution of process cooling loads is very different than in buildings. • Customized seasonal efficiency indicators allow for reliable estimation of energy saving. The food sector is a major consumer of energy and growing efforts are being made in the search for solutions that will guarantee the efficient and sustainable use of energy resources. Among the different sectors, wineries are attracting particular interest due to the continuous growth of the global market and production. Surveys conducted in the winemaking sector have highlighted the importance of performing accurate energy audits and have identified the installation of efficient refrigeration systems as a promising solution in a variety of cases. Unfortunately, the savings achievable by efficient cooling technologies are often estimated using simplified approaches which do not take into consideration the actual operating conditions of the equipment typically variable on seasonal and daily bases. In this paper a novel bottom-up procedure is presented, aimed at developing reliable profiles for refrigeration and air-conditioning loads and at assessing the extent to which more efficient chilling units could contribute to reducing electricity consumption. The use of standard Seasonal Energy Efficiency Ratios is critically discussed and a novel customized indicator is proposed. The method is applied to a medium-scale winery producing still red and white wines and sparkling wines, for which only aggregated energy consumption data are available. After deriving detailed load profiles, it is proven that the use of standard seasonal indicators leads to 56.85% and 83.87% overestimation of potential energy savings, respectively, for low and medium temperature cooling energy uses, confirming the importance of adopting seasonal indicators customized on the actual operating conditions of chillers. [ABSTRACT FROM AUTHOR]

• Floating offshore wind turbines are the next frontier in the wind energy sector. • Life cycle assessment is crucial to the planning of floating offshore wind farms. • A cost model is developed for life cycle assessment of offshore wind farms. • CAPEX, OPEX and DECEX are considered in the model. • A case study of a wind farm located in Southern Italy is developed. Over the last few decades, there has been a renewed interest in the offshore wind sector. In particular, floating wind turbines represent the next frontier in the wind power industry. Currently, only research prototypes exist, and few studies are available on their possible investment cost. Therefore, a cost assessment for this technology is necessary to ascertain whether it is economically sustainable. This paper develops a life cycle cost model for floating offshore wind farms, bringing together the most up-to-date data and parametric equations from databases and literature. The cost model considers the key parameters of the wind power economy, namely CAPEX, OPEX, DECEX and LCOE. The proposed model should be helpful for future decision-making, as the wind energy industry is in constant evolution. An application to an offshore floating wind farms is also carried out, in which the three main types of floaters are considered, namely the Semi-Submersible Platform, the Spar Buoy and the Tension Leg Platform. An average LCOE of 9.74 € c / kWh was found, at the lower bound of the typical range applying to fixed base offshore wind farms, and higher than typical values applying to onshore wind farms. [ABSTRACT FROM AUTHOR]

• Cogeneration system proposal for a building in Pisa for sized and undersized modes. • Energy costs of the proposed system are evaluated and contrasted for Iran and Italy. • Proposed system payback period is obtained and analyzed for Iran and Italy by NPV. • For under-sized system, electricity cost is about 37% more than in sized system. • If natural gas price is taken the same as Iran, the payback period reduces by 6.4%. The objective of the present paper is sizing of a technically optimum and economically feasible cogeneration system to supply heating, cooling and electricity to a reference building in the city of Pisa, Italy, for different months of the year. This cogeneration system is proposed in two operational modes, sized and under-sized, so that the effect of natural gas and electricity consumption costs on the system design can be achieved. To this end, the amount of energy consumption and cost of various types of the proposed cogeneration systems based on reciprocating engines are computed and compared. Afterward, in the proposed systems, for understanding the effect of the costs of the energy carriers in different countries on the rate of payback period, a comparison is conducted on the payback period between Iran and Italy. In the end, a sensitivity analysis is performed in Iran and Italy to survey the effect of any change in the cost of investment, natural gas, and electricity on the payback period. The results indicated that although the costs of gas and electricity are comparatively lower, the payback period is longer for Iran, which can be blamed on Iran's higher discount rate (~50%). The results of sensitivity analysis showed that if the natural gas cost in Italy equals that of Iran, there would be a 6.4% reduction in the payback period and if the electricity cost consumption in Iran is taken equivalent to the cost of electricity in Italy, a decrease of 25% will appear in the payback period. [ABSTRACT FROM AUTHOR]

• Various solar energy systems for combined heat and power provision are compared. • PVT CHP system has the highest total energy output and emission reduction potential. • PV system has the shortest payback time and the lowest levelised cost of energy. • ETC solar-thermal system is economically inviable for the sport centre application. • PVT CHP system attains the highest total cost saving if a carbon price is imposed. This paper presents a comprehensive analysis of the energetic, economic and environmental potentials of hybrid photovoltaic-thermal (PVT) and conventional solar energy systems for combined heat and power provision. A solar combined heat and power (S-CHP) system based on PVT collectors, a solar-power system based on PV panels, a solar-thermal system based on evacuated tube collectors (ETCs), and a S-CHP system based on a combination of side-by-side PV panels and ETCs (PV-ETC) are assessed and compared. A conventional CHP system based on a natural-gas-fired internal combustion engine (ICE) prime mover is also analysed as a competing fossil-fuel based solution. Annual simulations are conducted for the provision of electricity, along with space heating, swimming pool heating and hot water to the University Sports Centre of Bari, Italy. The results show that, based on a total installation area of 4000 m2 in all cases, the PVT S-CHP system outperforms the other systems in terms of total energy output, with annual electrical and thermal energy yields reaching 82.3% and 51.3% of the centre's demands, respectively. The PV system is the most profitable solar solution, with the shortest payback time (9.4 years) and lowest levelised cost of energy (0.089 €/kWh). Conversely, the ETC solar-thermal system is not economically viable for the sports centre application, and increasing the ETC area share in the combined PV-ETC S-CHP system is unfavourable due to the low natural gas price. Although the PVT S-CHP system has the highest investment cost, the high annual revenue from the avoided energy bills elevates its economic performance to a level between those of the conventional PV and ETC-based S-CHP systems, with a payback time of 13.7 years and a levelised cost of energy of 0.109 €/kWh. However, at 445 tCO 2 /year, the CO 2 emission reduction potential of the PVT S-CHP system is considerably higher (by 40–75%) than those of the all other solar systems (254–317 tCO 2 /year). Compared to the solar energy systems, the ICE-CHP system has the shortest payback time (6.2 years), but its CO 2 emission reduction (25 tCO 2 /year) is significantly lower. A high carbon price is beneficial for improving the cost-competitiveness of the solar energy systems, boosting its market penetration and helping to meet any carbon emission targets. [ABSTRACT FROM AUTHOR]

• Sizing and operation optimization of a hybrid energy plant. • Integration of life cycle assessment into optimization. • Non-linear life cycle inventory scaling of energy systems. • Estimation of the operational primary energy and cumulative energy demand. This paper deals with the optimal design of a hybrid energy plant, which can include the following energy systems: solar thermal collector, photovoltaic panel, hybrid photovoltaic/thermal solar system, combined heat and power system, organic Rankine cycle, absorption chiller, air source heat pump, ground source heat pump and thermal energy storage. Three different configurations are analyzed. In the first configuration, the abovementioned systems are considered with the exception of the hybrid photovoltaic/thermal solar system and organic Rankine cycle. In the second configuration, a hybrid photovoltaic/thermal solar system is also included and in the third configuration the use of an organic Rankine cycle as the bottoming cycle of the combined heat and power system is evaluated. The optimization goal is to minimize the primary energy demanded throughout the manufacturing and operation phase of the hybrid energy plant. The challenge of non-linear life cycle inventory scaling of energy systems is also addressed. A tower located in northern Italy is selected as a case study and two different approaches are evaluated. The first approach consists of solving the sizing optimization by minimizing primary energy consumption only during the operation phase, while in the second approach primary energy consumption is minimized throughout the life cycle of the plant by integrating the life cycle assessment into the optimization process. The results show that, if life cycle assessment is integrated, the optimal sizes of plant components are different and the primary energy saving throughout the life cycle is always higher. With reference to the LCA integrated approach and compared to the first configuration, the use of a hybrid photovoltaic/thermal solar system instead of separate solar thermal collector and photovoltaic panels is more efficient and may allow a primary energy saving of about 4%. Furthermore, compared to a conventional plant, the primary energy saving achievable with the first configuration is approximately 14%, while the primary energy saving increases to about 17% for the second and third configurations. [ABSTRACT FROM AUTHOR]